Increasing spectral bandwidth is one way to increasing channel capacity in telecommunications. For example, in order to increase channel capacity, the Institute of Electrical and Electronics Engineers (IEEE) amendment known as 802.11n for wireless local area network (WLAN) communication introduced allocating to a wireless network the combined bandwidth of two adjacent (contiguous) 20 MHz channels to provide 40 MHz of bandwidth. The wider bandwidth mode of operation of the wireless network is useful to achieve higher data rates. In the wider bandwidth mode, one channel is referred to as the primary channel and the other channel is referred to as the secondary channel.
Due to asymmetric channel access rules, wireless network devices using a 40 MHz operation mode have an unfair advantage under the rules of the IEEE 802.11n amendment. For example, according to the rules of IEEE 802.11n amendment, the secondary channel only has to be clear or free from transmissions during a time interval known as the Point Coordination Function Interframe Spacing (PIFS) instead of the longer time interval known as a Distributed Interframe Spacing (DIFS); or that backoff rules reflect the congestion level of the primary channel but are relatively insensitive to the congestion level of the secondary channel; or that reservation mechanisms on the secondary channel may be ignored; or that there are more relaxed Clear Channel Assessment (CCA) rules governing access to the secondary channel. These factors can allow devices operating in 40 MHz to cause unfair interference to those 20 MHz devices operating on the secondary channel.